1. Technical Area
The invention pertains to a device for producing at least two tubular belt bands which can be turned inside-out.
2. State of the Art
WO 98/51,845 describes a tubular band and a device for its production on a power loom. The power loom has a reed, the dents of which form a gap, which tapers down from the top toward the bottom. The reed can be moved up and down, as a result of which the warp threads arrive in areas where they are spread out to different degrees (areas of different density), so that a tubular band of varying width can be produced. For this purpose, it is also necessary that the fabric be guided by expanders along the two long edges, preferably immediately after the woof thread has been beaten. The widening effect of the expanders can be controlled in synchrony with, and essentially in proportion to, the increase or decrease in the distance between the warp threads. It is possible to produce a number of different seamless variants of this type of tubular band. For one of these variants, it is proposed that the tubular band be produced on a power loom as a wide, multiple-use fabric with a seam and that it then be cut into individual tubular bands by a thermal cutting device. Because of the considerable change in the density of the warp threads by the reed, however, there is considerable doubt that a usable wide fabric can be produced, since there is a considerable amount of additional compression and decompression between the adjacent tubular bands.
Aside from the fact that the device and the production method are extremely complicated, the density of the warp threads changes in correspondence with the degree of spreading by the reed, which means that structure of the fabric is looser in the wider areas than in the narrower ones. As a result, the tubular band which is obtained has a relatively coarse structure, especially in the wider areas, and its strength is also limited correspondingly. In particular, a tubular fabric of this type is not suitable as a belt band nor as an inflatable auto safety belt, because such belt bands must absorb longitudinal forces, that is, forces which proceed in the restraining direction. Because the arrangement of the warp threads varies with their density, the threads are neither parallel to each other nor straight, as a result of which longitudinal forces cannot be absorbed efficiently; on the contrary, they cause a change in the length and/or a deformation of the belt band. In addition, the hem of the tubular band is on the outside, which is not only unsightly but also dangerous because of its hard edge, which can cause injury.
A woven belt band which is suitable as an inflatable belt band for auto safety belts is described in WO 99/40,247. The disadvantage here is that this fabric either must be woven as a round fabric or it must have two woven layers, which are connected to each other along at least one side by a woven hem. The belt band must be assembled to form several layers by a complicated process, not only to make it suitable as a belt band but also to hide the unsightly and dangerous hem.